1. Field of Invention
The present invention relates to a method for patterning a metal layer. More particularly, the present invention relates to a method for patterning a metal layer that is formed on a metal oxide layer.
2. Description of Related Art
Etching processes have been widely used in manufacturing semiconductor device, microelectric mechanic system (MENS), display device and other electronics. Typically, etching process may be classified as two types, dry etching and wet etching. The manufacturer may choose dry etching process or wet etching process depending on the material and the critical dimension.
In wet etching processes, a material is dissolved in the etchant solution by chemical reactions. Therefore, wet etching is advantageous in low cost. However, the wet etching process is isotropic, and is difficult to be applied in fabricating a feature with a high aspect ratio. In addition, the layer, which is desirably etched, must have a different chemical property from adjacent layers to prevent the etchant from damaging the adjacent layers.
In dry etching, ions or particles bombardment are employed. Conventional dry etching processes include plasma etching and reaction ion etching. Dry etching processes may be applied in a feature with a high aspect ratio, and therefore is widely used in semiconductor industrial. For example, through holes in dielectric layers are often fabricated by dry etching processes. However, an etching stop layer is required in dry etching process in order to obtain a better etching profile and uniformity.
In some cases, typical etching processes may not be successfully used. For example, when a metal layer is directly formed on a metal oxide semiconductor layer, conventional etching processes may not successfully be used to etch the metal layer because etchant would damage the metal oxide semiconductor layer. In particular, the metal oxide semiconductor layer has a similar property with the metal layer. When a conventional etching process is employed to etch the metal layer, the metal oxide semiconductor layer would be damaged at the etching endpoint. Therefore, the final semiconductor device has a poor performance.
In view of the above, there exits in this art a need of improved method that is free of the aforementioned problems.